Homemade brake

I wanted to make a homemade brake for bending small sheet metal things. (I have a press). I think that the concept is straightforward,
however, I would like to know if there is any sort of a table that tabulated bending effort per inch of the width of metal being bent, depending on thickness.
Also, for the dies, would it be more proper to use high speed steel as opposed to mild steel (for strength).
Thanks
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Look for a thread stated by me with a great response from Nick Mueller about 6-12 months ago.
I can't find it on short notice but he suggested a urethane insert similar to this http://cgi.ebay.com/1-X-12-URETHANE-INSERT-FOR-1-BOTTOM-DIE_W0QQitemZ7556901674QQihZ020QQcategoryZ41957QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
only better. Then make everything from plain old cold rolled steel.
Karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Are you thinking a press brake? http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_479830_479830
Capacity is heavily dependent on the shape of the dies and especilly the width. Narrower gives you a sharper bend at the expense of higher required tonnage and more die wear.
Most of the shop built units I've seen for a 12 or 20 ton shop press use heavy wall angle iron. Professional press brake dies are all hardened tool steel. If you could find a 12" section of old press brake die, that would be perfect.
Keep in mind that the work needs to be perfectly centered under the cylinder.
Ignoramus24341 wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mine: http://www.metalworking.com/dropbox/_1998_retired_files / see brake1.txt and the associated jpgs. JR Dweller in the cellar
Ignoramus24341 wrote:

--
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I made a brake using the HF 20T press & air-over jack. Works well - the old "I don't need it often, but when I do, it's really nice to have".
- for the male die:
http://home.comcast.net/~bobengelhardt/brake1.jpg
- for the female, I used 1/2" rd bars side by side (the pic is rather cluttered, sorry):
http://home.comcast.net/~bobengelhardt/brake2.jpg
- the fence is really nice - it can be hard to align your scribed bend line with the die's edge
- the press's table & arbor were pretty loose. As a plain press that's fine, but for braking it can be a problem. I installed adjusters to keep the table and arbor aligned:
http://home.comcast.net/~bobengelhardt/brake3.jpg
As usual, I was motivated to use the material that I had & keep it simple (e.g., there was no milling involved).
The most-needed improvement is a speed-up for the no-load travel. The press has to open wide to get the bent piece out and then close up for the next bend. It's putt-putt-putt- ... . There was a thread where Ernie modified his jack to do this.
For box bending it would be nice to have a set of long-reach male dies of various lengths. I do have one shorter die (the one in the brake1 pic). I can do a step-wise box bend (partial bend, move over, repeat), but it's tedious.
I wasn't used to building for these kind of forces and had to add reinforcing to the table and more weld generally.
Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.